In theory, Sensus should offer sufficient security and privacy for
most polling needs, however, it has not been very well tested (and
the current implementation is kind of clunky and won't scale).
If you would like to
try it anyway and you live in the United States or Canada) you
may download the Sensus software and give it
a try.

If you're looking for a simple email voting system
with minimal
security and no encryption, you may want to take a look at some
Perl scripts my husband and I hacked together to run our graduate
student government election.